Joining unit

Abstract

A joining unit contains a spindle drive in the form of a hollow shaft motor that encloses a spindle. The hollow shaft motor serves to achieve a linear movement of a joining tool for the execution of a joining process. The joining unit contains instruments for the presetting and / or determination of the forces exerted and / or the movement of the joining tool during the joining process.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to International Application Serial No. PCT / EP2006 / 007029 filed Jul. 18, 2006.TECHNICAL FIELD[0002]The invention relates to a joining unit according to the main part of claim 1.BACKGROUND[0003]A joining unit of this type is known from DE 203 05 789 U1.[0004]The joining unit described therein contains a spindle drive for the generation of a linear movement of a joining tool. The spindle drive is formed by a hollow shaft motor that encloses a spindle.[0005]The hollow shaft motor is embodied as an electric drive and encompasses a stator as well as a rotor which is firmly attached to the spindle. The rotor causes the spindle to execute a rotational movement.[0006]For the generation of the linear movement of the joining tool a plunger is provided that forms the lower surface of a tubular housing insert having an interior space through which a portion of the spindle extends. A nut is provided at the upper side o...

AI Technical Summary

Benefits of technology

[0012]The object underlying the present invention is a joining unit of the type mentioned in the beginning that not only has a high functionality and safety of use but also a simple and cost-effective construction.

[0016]Because the spindle drive according to the invention is embodied in the form of a hollow shaft motor no gearing is necessary for driving the joining tool so that the joining unit has a small overall installed size and can be fabricated at reasonable costs. Moreover, a drive of this type can be well controlled and its dynamics are high. In addition, no constraint as to the rotational speed on the input side is exercised during the operation of such a gear-less drive. And, because there is no gear there is the additional advantage of having one less wear part that would require maintaining. In general, since a gear always has a certain gear play a higher positioning accuracy can be achieved by using joining units that have gear-less drives than by using systems which function with gears.

[0021]Furthermore, a closed-loop force control can be integrated into the controller which serves to prevent damages to components of the joining units in the case of high force spikes. It is particularly advantageous to perform the closed-loop force control in a manner that in addition to a closed-loop velocity control also the target position that has to be approached by the joining tool as predetermined in the currently activated position set will be adjusted against the current processing direction. In this manner, reversing the direction of the joining tool is initiated and, thus, a collision of the joining tool with an obstacle is prevented.

[0022]The closed-loop force control is integrated in the controller of the electric drive so that no external units are required for this purpose and a quick execution of the closed-loop force control is ensured.

[0023]In a particularly advantageous embodiment the joining unit comprises a limit stop switch-off that results in a shut-off of the electric drive in the case of unacceptably high forces and thus protects the joining unit from damages. It is particularly advantageous if the limit stop switch-off contains the spring bearing of a force sensor whereby unacceptably high forces can be sensed by deflection of the spring bearing. The limit stop switch-off formed in this manner not only has a simple and robust construction but at the same time protects the force sensor from damages.

[0025]It is particularly advantageous if the joining unit has a modular construction with respect to its mechanical components. In particular, modular entities are formed by the housing that accommodates the electric drive and the spindle and by the spindles so that the joining unit can be configured for different strokes of the joining tools without any effort.

Problems solved by technology

It is an essential disadvantage of such joining units that the functional control thereof is primarily performed via external units.

Due to the time required for the processing of the signal in the external unit as well as the time for signal transmission between the joining unit and the external unit it may be possible that the emergency shut-off is not actuated in time thus resulting in damages of components of the joining unit due to excessive straining by force.

Moreover, a system in which essential control functions are performed by external units is relatively complex and, therefore, difficult to handle by the user.

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